The present disclosure is generally related to screening methods for therapeutic agents for Friedreich's Ataxia. More particularly, the present disclosure relates to a cell-based model exhibiting metabolic characteristics of Friedreich's Ataxia and methods of screening therapeutic agents for treating Friedreich's Ataxia.
Friedreich's Ataxia (FRDA) is an autosomal recessive mitochondrial disorder caused by a homozygous triplet nucleotide repeat expansion in intron 1 of the FXN gene located on chromosome 9q21.11. This intronic expansion causes impaired transcription of the FXN gene and, consequently, a pathological deficiency of the FXN gene product frataxin. Frataxin is targeted to the mitochondrial matrix, where it is known to act as an iron-binding protein and participates in the proper assembly and function of iron-sulfur cluster (ISC) dependent proteins including complexes I, II, and III of the respiratory chain and aconitase of the tricarboxylic acid (TCA) cycle. Thus, frataxin deficiency severely compromises both cellular respiration and overall mitochondrial function leading to energetic stress and adenosine triphosphate (ATP) deficiency. Although patients develop multisystem diseases including early spinocerebellar degeneration, ataxia, and diabetes, the primary cause of death is heart failure for nearly 85% of those afflicted. Similarly, although the phenotypes of the neuron-specific enolase (NSE) and muscle creatine kinase (MCK)—Cre conditional mouse models of FRDA differ, both models develop a fatal cardiomyopathy and impaired activity of iron-sulfur cluster-dependent respiratory complexes consistent with the human disease.
Frataxin protein levels have a narrow range of efficacy for study. Heterozygote conditions for the disease have no phenotype in animals or cells in culture, and heterozygous patients have no FRDA disease. This indicates that cells are able to function in a non-disease fashion across a wide range of frataxin concentrations. However, when frataxin levels are reduced too greatly, the cells die rapidly.
Accordingly, there is a critical unmet need for novel materials and methods for studying the FRDA disease phenotype and screening for therapeutic development.